Tuesday, January 12, 2010

Haiti Earthquake - Fun Facts

Here we are, at the exact moment where we know about an earthquake, but not all the causalities. I'm expecting a horror story.

First of all, the Caribbean Plate is an amazing anomaly. Nobody knows how it came about, or exactly what it is doing. It is a big hunk of lower density rock, so it does not sink back into the netherworld (subduction). It may have been torn off something, or it may be the barf of a giant Atlantic hotspot. Nobody knows.

The oceanic crust of the NA plate is denser, so in a crunch, it is going down on the east side, but probably not without a fight. All the lovely volcanoes are on that edge. The northern edge has to 'slide' in a transform fault, like the San Andreas. This earthquake was on a transform fault, towards the inside of the boundary. The fault plane solution is mostly strike-slip, with some thrust, so it really is a standard San Andreas, and not a thrust. That might lower some damage potential. I don't know how well the crust carries a seismic wave, which will influence how far the damage extends.

The Caribbean Plate has had a rough time, that's why all the crumpled rock around the edge. It's still a mystery, but although the arrows show it moving east, it is actually moving west, but slower than the NA plate. I'm sure the big fault motions (like this one) have to be half slide, and half thrust, in order to build up those mountains, which are really islands. Without the earthquakes, these islands wouldn't exist!

Somebody has objected to my use of the world 'fun' as applied to this horrible tragedy. This post was just on geology, and was written in that big gap before we knew anything about the death toll. Besides, I can only laugh or cry, and I put out the black humour. :)()()(